Method of rendering fabrics water repellent



United States Patent METHOD OFIRENDERENG FABRICS WATER REPELLENT William R. Collings, Midland, 'Mich., assignor to Dow Corning Corporation, Midland, Mich., a corporation of Michigan No Drawing. Application March 16, 1953 Serial N0. 342,738

5 Claims. (Cl. 28-74) This invention relates to a method of rendering cellulosic fabrics water repellent. e

The treatment of fabrics with organosilicon compositions in order to render them waterv repellent has been employed commercially for some years. This treatment produces a water repellent film on the fabric which is invisible and which does not affect the hand or drape of the fabric. In general, this water repellency is resistant to laundering and to dry-cleaning. However, the durability of the water repellency on cellulosic fabrics, particularly cotton, is in general less than on other type fabrics. Since cotton fabrics account for a major portion of all washable fabrics sold, it would be highly desirable to improve the durability of the water repellency of these fabrics.

Accordingly, it is the primary object of this invention to improve the life of thewater repellent character of cellulosicfabrics which have been treated with organosilicon compounds.

In accordance with this invention, a cellulosicfabric is treated with an organosilicon composition, thensubjected to compressive shrinkage and thereafter heated at a temperature of at least 100 F. until the siloxane is cured.

In this invention, compressive shrinkage of the fabric may be accomplished in any convenient manner. For example, the cloth may be compressed by means of stenters or by holding the fabric against a sheet of an elastic material as the surface of the sheet adjacent to the cloth is alternately expanded and contracted. As the surface of the elastic material contracts, the fabric is thereby compressed so that the weft threads are pressed close together causing the warp threads to assume a more sinuous configuration. Compressive shrinkage is used primarly to prevent shrinkage of cellulosic fabrics during washing.

The two primary commercial modifications of compressive shrinkage are the well known Sanforizing process in which the fabric is held against a wool blanket and the well known Rigmel process in which the fabric is held against a rubber sheet. In both of these modificaice I to 5 percent by Weight of thelorganosilicon composition based on the Weight of the fabric. More than 5 percent by weight may be applied if desired although excessive amounts of the organosilicon compounds tend to alter the hand and drape of the fabric.

Organosilicon compositions which are operative in this invention include all hydrolyzable silanes, alkali metal salts of organosila'nols and siloxanes, having on the average from 1 to 2.5 monovalent hydrocarbon radi cals per silicon atom. The silanes which are operative herein include, for example, monomeric silanes such as dimethyldichlorosilane, monomethyltriethoxysilane, ethyldiethoxysilane, octadecyltriacetoxysilane, trimethylchlorosilane, vinyldiisopropoxysilane, phenylmethyldimethoxysilane; polymeric silanes such as methylsilazanes, methylpolysilanes containing SiSi linkages such as dimethyltetramethoxyisilane and silcarbanes such as- Me (C H O)SiCH Si(OC H )Me g and siloxanes such as methylhydrogensiloxane, 'dimethylsiloxane, monomethylsiloxane, octadecylmethylsiloxane, octadecylhydrogen siloxane, 'phenylhydrogensiloxaue and mixtures and copolymers of dimethysiloxane and methylhydrogensiloxane, ethylhydrogensiloxane and trimethylsiloxane, and butylhydrogensiloxane and dimethylsiloxane; and alkali metal salts of 'organosilanols such as MeSi(ONa) EtSiO OK) C H SiOOLi,

' Meg NaO (SiO ),.Na

and mixtures thereof.

It is to be understood that the organosilicon compounds employed in this invention can be any combination of the ab'ovedefined hydrolyzable silanes, siloxanes and tions, the cloth is usually wet with water prior to comprior to compressive shrinkage of the fabric. This can be done in any convenient manner. For example, a liquid organosilicon compound or a solution or an emulsion of an organosilicon compound can be sprayed onto the fabric or the fabric can be dipped into a liquid organosilicon compound or into a solution or an emulsion of an organosilicon compound. Alternatively, the fabric may be exposed to the vapors of a volatile organosilicon compound.

The amount of organosilicon compound applied to the fabric can be varied to suit the particular use to which the fabric is to be put. In general, satisfactory water repellency is obtained when the fabric contains from 1 alkali metal salts. Thus, for example, the organosilicon compounds which are operative herein include partially hydrolyzed alkoxylated siloxanes and partially hydrolyzed alkoxylated siloxanes which contain SiSi linkages and SiCSi linkages such as those obtained by alkoxylating the distillation residue from the reaction of methylchloride and silicon. The preferred compounds for use in this invention are combinations of methylsiloxanes and methylhydrogensiloxanes such as those which are particularly described in U. S. Patent 2,588,365.

If halosilanes are used in the method of this invention, care should be taken to neutralize the by-produced halogen acid immediately after applying the silane to the fabric. 7

After the fabric has been treated with the organosilicon compound and subjected to compressive shrinkage, it is then heated in any convenient manner at a temperature of at least F. This serves to cure the organosiloxane. Preferably, the treated fabric is heated at temperatures of 300 F. to 450 F. or higher.

Fabrics which are processed in accordance with this Example 1 When a cotton fabric is fed from a feed roll through a steamchamber (to wet and soften the fibers) and then through a 2 percent by weight aqueous solution of a sodium salt of monomethylsiloxane having 1.2 sodium atoms per silicon atom, and then through a 5 percent by weight acetic acid solution and the cloth is then sprayed with water to remove any electrolyte, such as acetic acid and sodium acetate, and passed onto a moving endless .4 inch thick wool blanket, and the cloth and blanket are then passed around a 2 inch feed roller which is provided with an electrically heated shoe so positioned a that as the cloth and blanket are passed around the roller the former is pressed firmly against the latter and the cloth and blanket are then passed onto a Palmer drying drum which is locatedadjacent to the feed roller and revolves in the opposite direction and the cloth is then removed from the blanket and heated in a tenter at 325 F. for /2 hour, the resulting fabric is water repellent and contains about 2'percentby weight siloxane.

Example 2 Example 3 When the process of Example 1 is repeated except that the cloth is passed through an atmosphere of the vapors of methyldiethoxysilane and dimethyldiethoxysilane in amount of 75 parts by volume of the former and 25 parts by volume of the latter, the concentration of the vapors being such as to give a 2 percent by Weight pick-up of methylsiloxanes on the fabric, the resulting fabric is water repellent and does not shrink whenwashed.

That which is claimed is: a t

1. The method of rendering cellulosic fabrics'water repellent which comprises treating the fabrics with an organosilicon composition of the group consisting of hydrolyzable silanes, alkali metal salts or organosilanols and siloxanes, said organosilicon composition having on When a cotton fabric' is passed 1 the average from 1 to 2.5 monovalent hydrocarbon radicals per silicon atom, subjecting the fabric to mechanical compressive shrinkage and thereafter heating it at a temperature of at least 100 F. until the organosilicon compound is cured. V

2. The method in accordance with claim 1 wherein the fabric is a cotton fabric.

3. A method of rendering cotton fabrics water repellent which comprises treating the fabric with a methylhydrogenpolysiloxane having on the average from 1 to 2.5 methyl groups per silicon atom, subjecting the fabric to mechanical compressive shrinkage and then heating it at a temperature of at least 100 F. until the siloxane is cured.

4. A method of rendering a cotton fabric water repellent which comprises treating the fabric with an alkali metal salt of a methylsilanol, said salt having on the average from 1 to 2.5 methyl groups per silicon atom,

subjecting the fabric to mechanical compressive shrinkage A and then heating it at a temperature of at least 100 F. until the siloxane is cured.

5. The method of rendering cellulosie fabrics water repellent which comprises wetting the fabric with water, treating the fabric with an organosilicon composition of the group consisting of hydrolyzable silanes, alkali metal salts of organosilanols and siloxanes, said organo silicon composition having on the average from 1 to 2.5 monovalent hydrocarbon radicals per silicon atom, subjecting thegfabric to mechanical compressive shrinkage and thereafter heatingit at a temperature of at least 100' F. until the organosilicon compound is cured.

References Cited in the file of this patent UNITED STATES PATENTS 2,338,983 Thackston et al Jan. 11, 1944 2,446,864 Abrams Aug. 10, 1948 2,474,704 Thayer June 28, 1949 2,519,232 Cruz Aug. 15, 1950 2,566,957 Pedlow et al. Sept. 4, 1951 I UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 2,833,022 May 6, 1958 William E. Collings It is hereby certified that error appears in the printed specification of the above numbered patent requiring correction and that the said Letters Patent should read as corrected below.

Column 2, line 17, for "dimethyltetramethoxyisilane" read --dimethyltetramethoxydisilane"-,-. v

Signed and sealed this 15th day of July 1958.,

(SEAL) Attcst:

'KARL H. AXLINE ROBERT c. WATSON Attestin Officer Commissioner Of Patents 

1. THE METHOD OF RENDERING CELLULOSIC FABRICS WATER REPELLENT WHICH COMPRISES TREATING THE FABRICS WITH AN ORGANOSILICON COMPOSITION OF THE GROUP CONSISTING OF HYDROLYZABLE SILANES, ALKALI METAL SALTS OF ORGANOSILANOLS AND SILOXANES, SAID ORGANOSILICON COMPOSITION HAVING ON THE AVERAGE FROM 1 TO 2.5 MONOVALENT HYDROCARBON RADICALS PER SILICON ATOMS SUBJECTING THE FABRIC TO MECHANICAL TEMPERATURE OF AT LEAST 100*F. UNTIL THE ORGANOSILICON COMPOUND IS CURED. 